Derivative Financial Instruments and Hedging Activities - Derivatives (Details) $ in Thousands, bbl in Millions	9 Months Ended	12 Months Ended
	May 31, 2019 USD ($) bbl	Aug. 31, 2018 USD ($) bbl
Derivative [Line Items]
Derivative Asset, Noncurrent	$ 22,300	$ 23,100
Derivative Liability, Noncurrent	14,700	7,900
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	251,648	316,545
Derivative Assets	281,878	352,029
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	30,230	35,484
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	273,494	397,288
Derivative Liabilities	308,087	445,755
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	4,363	12,983
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	$ 30,230	35,484
Credit Rating Agencies Threshold, Minimum	66.67%
CF Nitrogen LLC [Member]
Derivative [Line Items]
Annual Payment Receivable Contingent On Investment Credit Rating	$ 5,000
Embedded derivative asset	20,900
Foreign exchange derivatives | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	5,208	6,698
Derivative Assets	9,685	15,401
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	4,477	8,703
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	2,847	15,998
Derivative Liabilities	7,324	24,701
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	4,477	8,703
Derivative Asset, Notional Amount	868,900	988,800
Interest rate swap derivatives | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	4,479
Derivative Liabilities	713	9,452
Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	20,957	23,595
Derivative Assets	20,957	23,595
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0	0
Commodity derivatives | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	225,483	286,252
Derivative Assets	251,236	313,033
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	25,753	26,781
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	270,647	381,290
Derivative Liabilities	300,763	421,054
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	4,363	12,983
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	25,753	$ 26,781
Fair Value Hedging | Interest rate swap derivatives | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Notional Amount	$ 495,000
Cash Flow Hedging
Derivative [Line Items]
Aggregate notional amount of cash flow hedges (in barrels) | bbl	8.2	1.1
Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	$ 5,547	$ 812
Derivative Liabilities	$ 14,692	$ 634